A Test of Endurance
by oneshotthot
Summary: (Oneshot Smut) Sick and tired of Sonic barging into his apartment unannounced trying to find Saitama, Genos agrees to make a deal with him. Since they find themselves evenly matched in combat, the two of them engage in a very different method of battle to determine who has the better endurance. (Genos/Sonic)


"Listen here, you smug punk," one metallic arm grasped tightly around Sonic's slim wrists, pinning him to the wall of the freshly cleaned apartment. He grinned back at the very angry cyborg, both of them fully aware that the ninja could slip out of his grasp at a moments notice, if he wanted to. "I have had just about enough of your uninvited appearances at our apartment, Master Saitama is not home, and even if he was, he would not want to waste his time on the likes of you."

"Oh it's _our_ apartment now, is it?" Sonic purred from beneath the younger man's grip. "I was under the impression that you simply stalked him and then after showing him how pitifully you can fight, he felt sorry for you and made you his pupil." Genos snarled at the man in front of him, tightening his grip. Sonic could swear that he saw the yellows of his irises glowing.

"You are the stalker!" the cyborg was becoming noticeably flustered, hot steam beginning to ooze from between his ridges as he moved his face closer to Sonic's. "And besides, I may be pitiful compared to master, but I could still beat you."

"Oh, really? is that so?" The ninja teased, grinning playfully as he slipped out of Genos's grasp and appeared behind him in a flash. "I seem to remember that the last time we fought your precious master had to step in and save you."

"Tch," Genos bit his lip, letting memories of his near defeat flood back into his mind. He shook them away quickly. "With my new parts, I would wipe the floor with you." Genos raised his hand, an orb in the middle lighting up as he fired up his incineration cannons threateningly. "When i'm done with you, there will be nothing left." Sonic rolled his eyes, darting behind the cyborg once again, knocking over a vase as he leapt past.

"Of course, you may have big cannons..." he paced up to Genos's scowling face slowly, making sure to knock over as many bits of furniture and trinkets onto the floor as possible. The cyborg froze as Sonic got so close that their noses were almost touching, and they could feel each other's warm breath on their faces. "But how can you win a fight against me when you can't even hit me." Genos swung his fist hard and fast into Sonic's face, only to realise, too late, that he had dodged it with ease.

"You have made a mess of our apartment, I really am going to destroy you now," his voice was low and serious.

"Yeah maybe you should clean that up, it really is all you're good for." Sonic could see the cyborg's rage growing with every comment, and he revelled in the fact that it was so easy and enjoyable to wind him up like this.

"That is it." The cyborg flew at Sonic with the force of a meteor, and Sonic purposely didn't dodge his attack, instead he let the two of them fall backwards over the sofa, landing in a heap on the floor. "Tch!" Genos flung himself up onto his knees, pinning Sonic to the ground as his core whirred at full force in his chest. "I am going to incinerate you, I am much more powerful than you are."

"And I'm much, quicker. Let's face it, I'm as quick as you are strong." Sonic sighed, growing bored of the thought of having to fight Saitama's annoyingly devoted pet again instead of his rival. Genos sighed in acceptance, the two were evenly matched in combat.

"If we fought for long enough, I could beat you with endurance alone, I am a cyborg after all." Genos said in a seductive, shifting more of his body onto Sonic's in an attempt to hold him down so he couldn't slip away again.

"Endurance!? Don't be dumb, your parts would start breaking before I would tire."

"Let's find out, Sonic. Either get out of our apartment or fight me now. I will give you a choice."

"Ugh!" the ninja sighed under the Cyborg's warm grasp, "we don't have time for that, it would get so boring. I couldn't bear to look at you for that long."

"I got sick of looking at you the moment you entered the room." The harsh words that made Genos seethe with rage, made Sonic smile like a cheshire cat.

"I have a more... interesting way to see who has the most impressive endurance."

"What do you m...?" Genos was interrupted by the man underneath him grinding his hips upwards and into his own. He unwillingly released a bout of hot steam out from between the ridges on his shoulder blades, which made Sonic smirk up at him with a smug look on his face.

"So here are the rules," the ninja continued to move his hips in a rhythmic motion as he spoke. "Whoever… finishes first, loses."

"And if I win, you will leave me and master Saitama alone and go and get a life." Sonic was slightly taken aback by the comment, but he hid it well. With one swift motion, he flipped Genos over onto his back, straddling him. He leant in close to the younger man's face and ran his tongue over the warm metal of his neck.

"When i'm done with you, you'll be calling _me_ master." Sonic's voice flowed smooth like syrup from between his lips, he nipped at the blonde's neck gently, letting hot breath enter his ear. Genos pretended not to be affected, but the older man could hear his core whirring faster and faster by the second. Sonic ground down into the cyborg's crotch, feeling a little uneasy as he wasn't too sure how cyborg anatomy worked when it came to sex. Soon enough however, he could feel the hardness growing beneath him, and he knew that he was doing what he needed to. The effects were not lost on the ninja though, and he too could feel a tightness in his pants. "Fuck," he whined under his breath. He looked down to see Genos smirking at him.

"Not as easy as you thought it would be, Sonic?" he teased. The ninja responded by pressing his lips against the others in a deep kiss, letting his tongue dart inside the cyborgs mouth. He was surprised to find that it was wet, and warm; not at all what he had expected. Genos kissed him back messily, his body becoming slightly overheated as his hands fumbled and grasped at Sonic's back.

"Awwwh, look at how flustered you're getting already," the older man grinned down, soaking up the rage from the mechanical eyes that stared up at him. "Will this be your first time?"

"Shut up," Genos spat back at him, his hands still exploring the curves and contours of Sonic's toned body.

"Heh, so you _are_ a virgin then," he teased, "I thought you would be saving your first time for your precious master." Genos's anger built up and his core whirred at the mention of Saitama, but he was caught off guard as Sonic's eager hand stroked and grasped at the bulge in his jeans. He let off a cloud of hot steam, that rested on Sonic's clothing, causing it to cling even tighter to his sculpted body.

"If you think that I am going to let you inside me, then you are sorely mistaken," the blonde hissed back at him. "I will not give myself to you in that way."

"So you are saving yourself for…HEY WHAT ARE YOU DOING….!?" Sonic gasped, enraged as Genos grasped the sides of his clothing and ripped it clean off his body, revealing the purple shapes and lines that decorated his slim, muscular frame. The golden irises scanned and zoomed into every part of the ninja's body, taking it all in. "You like my body, hmm?" he purred. The cyborg averted his gaze immediately, refusing to accept that there was anything that he liked about this infuriating man. "Don't look away," he demanded, taking Genos's face into his hand and turning it back to face him. Their eyes met in an innocent and magnetic connection for a moment before they remembered their situation.

With his goal in mind, Genos wrapped his hand around Sonic's length. His hand released something cool and wet as he began to move it slowly up and down. "What is that!?" Sonic yelled, both confused and aroused by the fact that Genos could produce his own lubrication.

"I need it for my joints sometimes," the cyborg replied, still working up and down the shaft hungrily.

"Dis… gus…. ting…" Sonic panted as erotic sensations began to flow through his body. "You seem pretty skilled to say that you've never done this before. Is this what you do to yourself when you think about your..." He was cut off by Genos's lips slamming down into his, his lips parted and their tongues fought for dominance.

A harsh tearing sound could be heard, and the raven haired ninja realised that it was the cyborg tearing off his clothing. Still sat on top of him, Sonic gazed down at the intricate machinery of his body, honestly impressed by it. He ran his hands down the smooth ridges, letting his fingers explore every dent and bolt on his broad chest and stomach until he finally reached the best part. The younger man gasped as Sonic began to pump up and down the length in rhythm with his own. The blonde bucked his hips upwards eagerly. "Now, now..." the ninja smirked, "be patient."

"Screw that," Genos frowned. He flipped the ninja over, taking him completely by surprise as he landed on his hands and knees.

"Hey!" he yelled in protest, secretly embarrassed that the boy was able to surprise him in that way.

"I am done messing around," the cyborg's voice was clouded by lust, "let's finish this." Without warning, Sonic could feel two mechanical fingers slide up inside him. He clenched his teeth and let out a low groan. The fingers moved in and out slowly, giving his body time to adjust to the feeling. He thought that this was a fairly considerate gesture for a man who supposedly hated him. "Ahhhh," he let out a lustful moan as the fingers hit a certain spot inside him. Genos smiled down at Sonic, taking in the sight of the usually smug ninja writhing and helpless below him. The sight gave him great pleasure.

"Are you ready for me now?" Genos asked.

"Yes, but one more thing..." Sonic moved forward to remove the fingers from inside him and turned to face the cyborg. "Let me be on top, ok?" Another bout of steam came out from between the plates on his chest and he nodded in agreement. "I want to see the look on your face when you lose."

The de-clothed man gently pushed the blonde down into a sitting position and straddled him. Their faces were inches apart, and Genos could feel long, black strands of hair tickling at the sensors on his neck. Their breathing was in-sync, and deep. Their eyes were locked in a hypnotic stare. "Ok," Genos said.

"Let the game begin." Sonic grasped at the length below him and slowly lowered himself down onto it. The two both moaned loudly in unison. "Nnngh..." Sonic waited until his body relaxed around the size of the cyborg, it was more than he was used to for sure, but Genos was patient. When he felt comfortable, he began to move up and down rhythmically.

"F-fuck..." Genos bit down on Sonic's lip as he began to feel euphoric sensations building up inside him. He grasped at Sonic's length and started working at it again in time with his thrusts. The sounds of their whines and groans echoed around the small room as the ninja repeatedly thrust downwards, letting Genos brush against his sweet spot.

"Y-you've got no chance of winning," Sonic taunted, watching as Genos twitched beneath him and the pleasure spread through him.

"With the noises you are making, I do not think that you can hold on for much longer." They were both right. As much as the two of them were desperately trying to hold back the feelings that burned inside them, it was becoming way too difficult of a task. They both cursed as Sonic quickened the pace, and Genos began to buck his hips upwards to meet the thrusts. It was all becoming too much. The fiery passion in their eyes kept them magnetised together, watching in awe as their expressions changed from those of anger, to determination, to pure pleasure. The sensations were coursing through their bodies like an electric current, bubbling up inside them like a shaken soda, ready to explode.

"No, fuck, I..."

"Agh, I can't..."

The sensation ripped through the both of them like pure ecstasy. Genos's fingers scratched and dug into the skin on Sonic's back, and the ninja's slim fingers tangled in blonde hair as they both climaxed together with a deafeningly load moan. Sonic let out his load into Genos's hand, and the two stared at each other in disbelief as they rode out the last few drops of pleasure from their orgasms. Their panting breaths slowly began to slow as they relaxed, Sonic still straddling the cyborg, who was still inside him.

"Again!" Sonic cried "We were seriously evenly matched again!?"

Bonus:

It was a particularly warm day in City Z, Saitama and Genos were strolling through the streets aimlessly. "It's pretty boring with no monsters around," Saitama sighed, pulling out the hem of his shirt in order to try and cool himself down.

"If you are bored, Master, we could always train. I must get stronger..." Genos noticed that Saitama's face was flushed and red from the excessive heat. "If you want, I can find a store and get you some ice cream, or a cold drink..."

"Hey, Saitama!" The two were interrupted by an all too familiar voice as a raven haired ninja jumped down in front of them. "If you're bored, why don't you fight me?" His face was twisted into an evil smile as he stared down the bald hero. "I think you'll be impressed with my new move, I perfected it just for you, it's called..."

"Hey Genos," Saitama interrupted. "You wanted to train right?" Genos's eyes widened, afraid that he knew what his master was going to say. "Fight Jack O Lantern Panic for me will ya."

"B-but Master... I"

"I'll head to the shop myself, have fun ok? Give him everything you've got." The two watched in annoyance as Saitama walked away, and then turned to each other. Genos let off a puff of steam and a crimson blush stained Sonic's cheeks as they both remembered the last time that they had seen each other.

"I suppose I'll have to deal with you first then," Sonic smirked. "Remember what he told you, sidekick. Give me everything you've got."

"I will be better than last time." The cyborg stated, a sly smile etched into his face.

"Well then bring it on."

"The apartment, in five minutes."

"I'll meet you there."


End file.
